Pressemeddelelse

Begravet dybt i hjertet af en kæmpe

1. juli 2015

Her er en farverig samling af gasarter og stjerner fanget med Wide Field Imager (WFI) kameraet på MPG/ESO 2,2 meterteleskopet på ESOs La Sillaobservatorium i Chile. Billedet viser en ung åben stjernehob med navnet NGC 2367. Det er en gruppe af babystjerner i centeret af en enorm og meget gammel struktur i kanten af Mælkevejen.

Det er den utrættelige observatør Sir William Herschel, som fra England opdagede hoben den 20. november 1784. Den klare åbne hob NGC 2367 befinder sig 7 000 lysår borte, i stjernebilledet Store Hund eller Canis Major. Hoben har kun eksisteret i omkring fem millioner år, så de fleste af stjernerne er unge og varme, og skinner med et intenst blåt lys. Det giver en flot kontrast til det bløde røde skær fra den omgivende brintgas i dette nye billede

Åbne hobe som NGC2367 er almindelige i spiralgalakser som Mælkevejen, og der er en tendens til, at de dannes i galaksernes ydre regioner. På hobenes vej rundt omkring de galaktiske centrum på virkes de af tyngdekræfterne fra andre hobe og af de store skyer af gas, som de bevæger sig tæt forbi. Åbne hobe hedder sådan fordi stjernerne i dem kun et løst bundne til hinanden. De taber konstant masse fordi noget af gassen bliver skubbet bort af strålingen fra de unge stjerner, og det bevirker, at nogle af stjernerne vandrer væk fra deres søskende, på samme måde som vi mener, Solen har gjort det for mange år siden. Efter få hundrede millioner år er de fleste åbne hobe spredt iblandt de andre stjerner.

Så længe de lever, kan hobene bruges som gode studieobjekter for stjernernes udvikling. Alle stjernerne i en given hob er dannet nogenlunde på samme tid, og ud fra den samme sky af stoffer, så det er nemmere at sammenligne stjernerne, og studere deres forskellige udviklingstrin.

Som så mange andre åbne hobe er NGC 2367 omgivet af den emissionståge, som stjernerne oprindeligt er dannet af. Resterne af tågen viser sig som strejf og skyer af brintgas, som ioniseres af de ultraviolette lys fra de varme stjerner,  og som derfor lyser op. Hvad der er mere usædvanligt for NGC 2367 er, at den tåge, som indeholder hoben igen er indeholdt i en langt større tåge - kendt som Brand 16, og den er igen blot en lille del af en enorm supershell, med betegnelsen GS234-02.

GS234-02 befinder sig ude i de yderste dele af Mælkevejen. Den er meget stor, med en diameter på hundreder af lysår. Den startede ved at en gruppe særligt tunge stjerner med kraftige stjernevinde hver dannede deres individuelle voksende boble af varm gas. Nabobobler slog sig så efterhånden sammen til en superboble. De korte levetider for disse store stjerner i centeret betød, at de alle eksploderede nogenlunde samtidigt som supernovaer, og det fik superboblen til at udvide sig endnu mere. Efterhånden smeltede den så sammen med flere nærliggende superbobler og dannede det, som kaldes en supershell eller superskal. Resultatet er en af de størst mulige strukturer i en galakse.

Et sådant system, som udvider sig i koncentriske skaller er med sin store alder og sin størrelse et find eksempel på de indviklede strukturer, som dannes i galakserne på grund af liv og død for de stjerner, som de indeholder.

Mere information

ESO er den fremmeste fællesnationale astronomiorganisation i Europa, og verdens langt mest produktive jordbaserede astronomiske observatorium. 16 lande er med i ESO: Belgien, Brazilien, Danmark, Finland, Frankrig, Italien, Nederlandene, Polen, Portugal, Spanien, Sverige, Schweiz, Storbritannien, Tjekkiet, Tyskland og Østrig, og desuden værtsnationen Chile. ESO har et ambitiøst program, som gør det muligt for astronomer at gøre vigtige videnskabelige opdagelser. Programmet har focus på design, konstruktion og drift af stærke jordbaserede observatorier. Desuden har ESO en ledende rolle i formidling og organisering af samarbejde omkring astronomisk forskning. ESO driver tre enestående observatorier i verdensklasse i Chile: La Silla, Paranal og Chajnantor. På Paranal driver ESO VLT, Very Large Telescope, som er verdens mest avancerede observatorium for synligt lys, samt to oversigtsteleskoper. VISTA, som observerer i infrarødt, er verdens største oversigtsteleskop, og VLT Survey Teleskopet er det største teleskop bygget til at overvåge himlen i synligt lys. ESO er en af de største partnere i ALMA, som er det største eksisterende astronomiprojekt. For tiden bygges E-ELT, et 39 m optisk og nærinfrarødt teleskop på Cerro Armazones, tæt ved Paranal. Det bliver "verdens største himmeløje".

 

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Dette er en oversættelse af ESO pressemeddelelse eso1526 lavet af ESON - et netværk af personer i ESOs medlemslande, der er kontaktpunkter for medierne i forbindelse med ESO nyheder, pressemeddelelser mm.

Om pressemeddelelsen

Pressemeddelelse nr.:eso1526da
Navn:NGC 2367
Type:Milky Way : Star : Grouping : Cluster : Open
Facility:MPG/ESO 2.2-metre telescope
Instruments:WFI

Billeder

Den farverige stjernehob NGC 2367
Den farverige stjernehob NGC 2367
Stjernehoben NGC 2367 i stjernebilledet Canis Major
Stjernehoben NGC 2367 i stjernebilledet Canis Major
Vidvinkeloptagelse af himlen omkring stjernehoben NGC 2367
Vidvinkeloptagelse af himlen omkring stjernehoben NGC 2367

Videoer

Zoom ind på stjernehoben NGC 2367
Zoom ind på stjernehoben NGC 2367
Den farverige stjernehob NGC 2367
Den farverige stjernehob NGC 2367

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